1. Field of the Invention
The present invention relates to cassettes having built in 2-dimensional array type radiation detection sensors.
2. Description of the Related Art
Radiation images typified by X-ray images have conventionally been used very widely in diagnosis of illnesses, non-destructive testing, etc.
The technology of radiating the X-rays that have passed through the photographed object onto a phosphor screen, exposing a silver halide film using the visible light generated from the phosphor screen, and obtaining a radiation image by chemically developing this film has a long history and has been contributing in a big way to the diagnosis of illnesses.
At present, in order to reduce the radiation dose, and to meet the requirements of compatibility with digital image processing, a technology has been widely adopted in which a latent image is formed by irradiating the X-rays that have passed through the photographed object onto an optically excitable phosphor sheet, and the X-ray image is read out by receiving the optically excited light emission produced by applying an excitation light such as a laser bean onto this latent image.
Further, in the recent years, even radiation imaging systems of detecting the X-rays that have passed through the photographed object using a radiation image detector that uses a semiconductor two-dimensional array type radiation image detection sensor have come into wide use.
This radiation image detector is very often used by enclosing it in a container that is usually called a cassette and that is a thin, lightweight, and is easy to carry box, so that it is very convenient for photographing a wide range of body parts quickly.
Photography using such a cassette type radiation image detector is different from the fixed position photographing equipment in that it is carried out by positioning the cassette appropriately to suit the condition of the patient who is the target of photography.
In such photography, since it is possible that the cassette is placed below the patient's body or, in some cases, since the patient is made to stand on the cassette, it is necessary to make the cassette have sufficient strength. In addition, there may also be unexpected accidents in which the cassette is dropped down to the ground while handling it.
Therefore, cassette type radiation image detectors used in this manner are required to have the strength to protect the radiation detection sensor inside the unit against static loads, and also to have shock resistance so that the internal radiation image detection sensor doe not get damages when the cassette is dropped down to ground.
For example, in Japanese Unexamined Patent Application Publication No. 2001-346788, concerning improvement of shock resistance, a proposal has been made of improving the shock resistance by providing shock absorbing material at the edges on the interior of the cassette. In addition, in Japanese Unexamined Patent Application Publication No. 2004-184679, a proposal has been made of filling the interior of the cassette by filler materials.
However, in a cassette type radiation image detector according to these proposals, the means for improving the shock resistance obstructs the size reduction and weight reduction desired of a cassette, or may also decrease the ease of assembly during manufacture or the ease of maintenance in the market.
The present invention was made in view of the above situation, and the purpose of the present invention is to provide a cassette type radiation image detector having a shock resistance that can protect the radiation image detection sensor sufficiently when the cassette is dropped, while at the same time not losing its small size and light weight.